Gas lasers and methods for operating them are generally known, for example, from DE 36 00 125 A1. Gas lasers typically include a fan for circulating the laser gas, the fan having a shaft, which is supported by means of at least one radial bearing and at least one axial bearing. In this instance, the bearings may be constructed as electromagnetic bearings. They have great bearing play and a sensor system, actuation system, and an electronic control system are generally provided to establish and control the position of the shaft in an axial or radial direction, since the bearings themselves do not set out any stable position of the shaft in an axial and radial direction. Known methods generally include corresponding logic loops for active control of the position of the shaft.
The shafts may also be constructed with gas bearings. Such a bearing is known from DE 36 00 125 A1. DE 36 00 125 A1 describes a fan for circulating large quantities of gas, in particular for high-power lasers. The fan has a shaft that is supported by two radial gas bearings and an axial gas bearing. The radial gas bearings are constructed as fish-bone air bearings that are supplied with air by a pump, which is formed by helical grooves at the lower side of a radial conveyor. These helical grooves at the upper end of the shaft also act as an axial gas bearing for the shaft. Gas is conveyed by the radial conveyor. In this instance, a problem arises that upwardly directed suction forces and the force of the axial gas bearing act on the radial conveyor. Downwardly directed gravitational force acts counter to these forces, and the two upwardly directed forces become increasingly dominant as the speeds increase. This problem is solved by the use of an additional axial magnetic bearing at the lower end of the shaft. In contrast, at low speeds, the gravitational force is dominant, which is a particular problem when turning the fan on or off. This problem is solved by the use of a compressed air pump, which is arranged to adjust an excess pressure at low speeds or an electromagnet.